The present invention relates generally to the game of golf and, more particularly, to golf club heads.
Modern golf clubs have typically been classified as either woods, irons or putters. The term xe2x80x9cwoodxe2x80x9d is an historical term that is still commonly used, even for golf clubs that are constructed of steel, titanium, fiberglass and other more exotic materials, to name a few. The term xe2x80x9cironxe2x80x9d is also an historical term that is still commonly used, even though those clubs are not typically constructed of iron, but are rather constructed of many of the same materials used to construct xe2x80x9cwoods.xe2x80x9d
Many advancements have been achieved, particularly over the past couple of decades, to make it easier to hit longer and straighter shots with woods and irons. In general, golf clubs are now designed to be more forgiving, so that shots that are struck less than perfectly will still have fairly consistent distance and directional control. Moreover, club heads now commonly are constructed of combinations of materials, to attempt to optimize the ball flight desired by a particular type of player.
One particular improvement that relates to irons is the use of perimeter weighting, whereby a disproportionate amount of the total weight of a club head is positioned behind and proximate the perimeter of the club head""s striking face, thereby creating a cavity immediately behind the striking face. The cavity is formed by the club face and the weight that is placed around and behind the club face. This type of club is typically referred to a xe2x80x9ccavity backxe2x80x9d iron. By moving the weight away from the center of gravity (CG) of the club head, the club is made to be more forgiving on off-center hits, resulting in more consistent distance and directional control. Further, perimeter weighting generally increases the moment of inertia about the club""s center of gravity, resulting in less twisting due to off-center hits, and more accurate shots.
Another improvement is the use of lighter and stronger materials, which enables club designers to move the CG to an optimal location on a wood or iron. Such a movement can make the club either easier to hook or to fade, if the movement is made either closer to or farther from the hosel. Similarly, if the CG is moved higher or lower with respect to the club face, the golf ball launch conditions can be altered. For instance, lowering the CG generally makes it easier to the get the ball airborne for either an iron or a wood. Conversely, raising the CG promotes a more boring ball flight that generally leaves the club face at a lower launch angle.
Generally, it has been shown that it can be advantageous for players with higher handicaps to use clubs with a lower CG. This is especially true for long irons, such as for example a 3-iron. Club designers have responded to this prospective advantage by lowering the CG of both woods and irons for clubs intended for higher handicap players. The most common way that this has been accomplished for irons is to move as much weight as possible to the area proximate the sole of the club. This results is a concentration of weight proximate the sole. Often, for these types of irons, the transition from the cavity to the weight on the sole is abrupt, compared to traditional irons having a smoother transition. When viewing a cross-section of the lower portion of the club face, a dramatic change in the thickness of the face nearer the sole often is apparent in such sole-weighted club heads.
While it is recognized that the lower CG of the improved clubs can be beneficial, such a lowering can have negative side effects. First, the concentrated mass proximate the sole can increase the stiffness of the club head. This can cause a noticeable change in the club""s feel. Feel is a term that is generally used by skilled practitioners to denote a subjective expression of the way a club feels to one""s hands when striking a ball, or the way it sounds. Feel is generally perceived as audible or tactile feedback to the golfer. Different sensations due to striking the ball in different locations on the club face may make a club less desirable to a potential user.
Second, the weight concentration proximate the sole can lead to different levels of flex at different points on the club face. The area of the face proximate the thickest portion of the sole is likely to flex less than the area proximate the thinner areas of the striking face. Such a change in flex can adversely affect performance.
Third, the weight concentration can lead to excess vibration, which can adversely affect the feel of the golf club, including the sound made by the club.
It should be appreciated from the foregoing description that there is a need for an improved golf club head that creates a more consistent flex when striking the ball, improves the club""s feel, and reduces vibration. The present invention satisfies this need and provides further related advantages.
The present invention provides a solution to counteract the negative side affects described above, by allowing club designers to design a club with an optimal center of gravity, while at the same time lowering the stiffness proximate the sole, creating more consistent flex while striking the ball, improving the feel of the club, and reducing vibration.
Generally, the present invention can be practiced using a variety of common club head shapes that are known in the art. Preferably, the club head comprises a unitary body that has a striking face and a sole. A recess is preferably formed in the sole that is adapted for receiving an insert. The preferred insert comprises a core and an intermediate layer. The intermediate layer generally is formed from a material that has a hardness and a modulus of elasticity that are lower than that of the core. The intermediate layer is generally disposed so that it partially encapsulates the core or fills interstices within the core. Three embodiments of the invention are shown and described below.
According to the first preferred embodiment of the invention, a set of cells are embedded proximate a sole portion of a preferred club head. The preferred club head comprises a body that has perimeter weighting and a cavity back. The cavity back may be either open or closed, such as for example in a hollow club head. The body is substantially similar to many cavity back clubs that are known in the art. The perimeter weighting of the preferred body forms a sole bar proximate the sole. The sole bar has an elongated slot that is formed or is cut therethrough, the slot extending between the toe and the heel of the body. Proximate the slot are a plurality of a apertures that are formed so as to receive a corresponding plurality of cells. The number of apertures may vary.
The cells each comprise a pin that is preferably encased in an elastomeric sleeve. The preferred cells, the apertures, and the preferred pins and sleeves are generally aligned so that their longitudinal axes are parallel with the striking face of the golf club head. Further, the longitudinal axes are preferably aligned generally parallel with the loft angle of a particular club.
During manufacture, the preferred cells are preferably inserted through the elongated slot, and sealed from the sole and held in place by a plug that is inserted into the slot so as to be flush with the sole upon completion of manufacture. The plug is held in place by conventional means known in the art, some of which are described below in the Detailed Description.
According to a second embodiment of the invention, a cartridge is used to provide the advantages described above. The preferred cartridge comprises a metal substrate having a plurality of interstices spaced therein. The interstices are preferably filled with a polymeric material.
According to a third embodiment of the invention, a cartridge is used to provide the advantages described above. The preferred cartridge comprises a metal substrate having a plurality of interstices spaced therein. A polymeric sleeve is preferably folded over a portion of the metal substrate. The preferred polymeric sleeve has nubs on an outer surface where contact is made with the club head body.
It is an object of the present invention to provide a golf club head that reduces club head stiffness.
It is a further object of the present invention to provide a golf club head that results in a more uniform face deflection in the hitting area.
It is a further object of the present invention to provide a golf club head that improves the feel of a golf club.
It is a further object of the present invention to provide a golf club head that absorbs energy.
It is a further object of the present invention to provide a golf club head that improves the weight distribution of a golf club.